gistfile1.fs

open System.IO

let  openFile =
     async { use  fs = new  FileStream(@"C:\Program Files\Internet Explorer\iexplore.exe",
                                     FileMode.Open, FileAccess.Read, FileShare.Read)
             let  data = Array.create (int fs.Length) 0uy
             let!  bytesRead = fs.ReadAsync(data, 0, data.Length)
             do  printfn "Read Bytes: %i, First bytes were: %i %i %i ..."
                 bytesRead data.(1) data.(2) data.(3) }

 Async.Run openFile